Gas discharge switching device

ABSTRACT

A gas-discharge switching device comprising: a hollow cathode in the form a closed chamber; a barrier dividing the above-mentioned chamber so as to form at least two discharge chambers; at least two anodes each of which is arranged within each of the discharge chambers: a means for arc firing.

[Jim States atet 1 Nastjukha et al.

[451 June 12, 1973 GAS-DISCHARGE SWITCHING DEVICE [56] References Cited UNITED STATES PATENTS 2,728,006 12/1955 Webster 313/217 X Primary ExaminerRoy Lake Assistant Examiner-James B. Mullins Att0rney.lohn C. Holman and Marvin R. Stern [57] ABSTRACT A gas-discharge switching device comprising: a hollow cathode in the form a closed chamber; a barrier dividing the above-mentioned chamber so as to form at least two discharge chambers; at least two anodes each of which is arranged within each of the discharge chambers: a means for arc firing.

2 Claims, 3 Drawing Figures [22] Filed: June 5, 1972 [21] Appl. No.: 259,952

[52] US. Cl. 315/338, 313/161, 313/162,

313/204, 313/217 [51] Int. Cl. H0lj 17/14 [58] Field of Search 315/334, 338;

Patented June 12, 1973 3,739,227

2 Sheets-Sheet 1 Patented June 12, 1973 3,739,227

2 Shoots-Sheet 2 a Z Q FIE] GAS-DISCHARGE SWITCHING DEVICE This invention relates to the field of electrical engineering and more particularly to gas-discharge switching devices.

Known in the present state of the art are gasdischarge switching devices with a hollow cold cathode in the form of a closed chamber and with the anode placed inside the above-mentioned chamber, such devices being used in various experimental physical and industrial installations, At currents over 100 kA and pulse durations shorter than 100 to 200 microseconds, these known devices lose their property of unidirectional conductivity. However, in cases where unidirectional conductivity is not essential, i.e., under oscillatory-discharge duty conditions, known devices are capable of switching S-kV currents as high as 300 to 350 kA. For example, gas-discharge switching devices are used under the above duty conditions in installations for forming and welding metal in an impulse magnetic field.

Experience acquired in the use of such devices in electric circuits of low inductance indicates that the maximum perimissible pulse current for normal service of the electrodes does not exceed 200 to 300 kA at a pulse duration of 20 to 100 microseconds. At current amplitudes exceeding the above values, the electrodes deteriorate rapidly, this being accompanied by excessive evolution of gases. As a result, the electric strength of the gas-discharge switching device worsens and its service life is shortened. Therefore, in cases when it becomes necessary to increase the current amplitude, recourse is made to parallel connection of the gasdischarge switching devices. Parallel connection not only lessens the current flowing through each of the devices, but is also advantageous in view of the fact that it lowers the total inductance of the parallel-connected devices. It should be noted, however, that parallel operation of several such devices calls for proper synchronization of their starting. This places more stringent requirements upon the firing facilities, requirements that are not always easily met. Moreover, the higher the frequency of the escillatory process of discharge, the smaller must be the scatter of firing of several parallelconnected gas-discharge switching devices.

Gas-discharge switching devices with a hollow cold cathode are fired by injecting the plasma of an auxiliary charge into the main discharge gap, this charge being produced in a special firing chamber or, alternatively, by means of an impulse magnetic field set up at shorttime connection of a solenoid surrounding the cathode to a source of direct current.

A serious disadvantage of the above-mentioned firing facilities is the relatively wide spread of the arc-firing time of the gas-discharge switching device. Thus, on starting a switching device by plasma-injection, the spread amounts to l 2 microseconds, and when firing the device by means of an impulse magnetic field, the spread is even wider and attains to microseconds. This disadvantage makes it impossible to resort to parallel connection of arc rectifiers in low-inductance circuits at current frequencies higher than 10 kc.p.s., since the considerable scatter of their firing leads to a significant distortion of the pulse waveform.

A primary object of the present invention is to provide a gas-discharge switching device of improved current-carrying capacity that can be used in lieu of parallel connection of several gas-discharge switching devices.

This object is accomplished by the development of a gas-discharge switching device filled with gas under a pressure corresponding to the left-hand branch of Paschens curve, comprising a hollow cathode in the form of a closed discharge chamber, an anode placed inside the above-mentioned chamber, and a means for firing the arc discharge, the above chamber being in accordance with the present invention 5 divided by a barrier into at least two discharge chambers, and the gas-discharge switching device being provided with at least one more anode arranged in such a manner that each of the discharge chambers contains the abovementioned anodes.

It is advantageous to make the discharge chambers communicating between each other.

The above and other object, features and advantages of the present invention will be further described in detail by way of example with reference to the accompanying drawings in which:

FIG. 1 is a general longitudinal sectional view of the hereindescribed gas-discharge switching device in accordance with the present invention;

FIG. 2 shows the shape of the impulse magnetic field within the discharge chamber;

FIG. 3 shows the connection diagram of the hereindescribed gas-discharge switching device and the oscillatory circuit.

The disclosed gas-discharge switching device comprises a hollow cathode formed by two metal casings 1 (FIG. 1) and a barrier 2. The barrier 2 divides the hollow cathode into two discharge chambers 3 that communicate with each other through a hole made in the barrier 2. The discharge chambers 3 contain metal anodes 4. The components of the hollow cathode the casings 1 and the barrier 2 are hermetically sealed together by means of packings 5. The anodes 4 are isolated from the cathode with the aid of insulators 6 and 7. The means for firing the discharge in the discharge chambers 3 consists of a solenoid 8 embracing the cathode and positioned in place by means of adjusting screws 9. The casings l and the barrier 2 are provided with communicating ducts 10 for cooling the cathode and the hollow current-supply terminals 11 of the anodes. The air is drawn out of the discharge chambers 3 through duct 12 provided in the barrier 2 and the collector 13 of the forevacuum pump (not shown in the drawing). A metal shield 14 is placed between the cathode casing l and the anode 4 for switching currents of 20 to 25-kV voltage. The distances of the anode 4 to the shield 14 and of the shield 14 to the cathode casing l are selected so that the electric strength of the gaps will be sufficient to prevent the occurrence of discharges within them. The shield 14 is provided with a terminal 15 for connecting external voltage dividers (not shown in the drawing). The terminal 15 is isolated from the cathode casing 1 by means of an insulator 16.

For normal operation of the gas-discharge switching device the dimensions of the cathode (i.e., the diameter a, in centimeters, of the chamber (FIG. 2) and the distance d, in centimeters, of the anode to the barrier), as well as the pressure p, in mm Hg, within the chamber must comply with the following requirements:

pd (pd)min for conformity with the values of the lefthand branch of Paschens curve;

a'p 1 for obtaining the hollow cathode effect.

l) is set so as the meet the above-stipulated first requirement. In order to fire the gas-discharge switching device connected to the oscillatory circuit with a sectionalized capacitor battery made up of capacitors 17 and 18, it is necessary to supply a current pulse from a 150 to 300 V source of direct current to the solenoid 8. The resulting field set up within the discharge chambers is of such a shape that the magnetic lines of force thread twice through the cathode in each discharge gap without passing through the anode 4 (FIG. 2). On application of a positive voltage to the anodes 4, the intersection of the electric and magnetic lines of force within the discharge gaps produces a potential traps inside which the electrons are subject to an oscillatory motion along the magnetic lines of force and, at the same time, drift along the axis of the anode-cathode systems. Moving for a sufficiently long period of time, these electrons ionize the gas under conditions at which the length of their free path is much greater than the length of the discharge gap. The ionization produces a discharge simultaneously in both discharge gaps. This is also promoted by the penetration of plasma from one of the discharge chambers 3 into the other one through the hole in the barrier 2 (FIG. 1). Measurements show that the spread of the firing time of the discharges produced within the discharge chambers is confined to 0.1 microsecond. The presence of two simultaneously operating discharge gaps within the gas-discharge switching device leads to a two-fold reduction in the inductance and resistance as compared with are rectifiers of conventional design.

What is claimed is:

l. A gas-discharge switching device filled with gas under a pressure corresponding to the left-hand branch of Paschens curve, comprising: a hollow cathode in the form of a closed chamber; a barrier dividing the abovementioned chamber so as to form at least two discharge chambers; at least two anodes each of which is arranged within each of the discharge chambers obtained as a result of division by the above-mentioned barrier; a means for are firing.

2. A gas-discharge switching device as claimed in claim 1, wherein the discharge chambers obtained as a result of division by the above-mentioned barrier communicate between each other. 

1. A gas-discharge switching device filled with gas under a pressure corresponding to the left-hand branch of Paschen''s curve, comprising: a hollow cathode in the form of a closed chamber; a barrier dividing the above-mentioned chamber so as to form at least two discharge chambers; at least two anodes each of which is arranged within each of the discharge chambers obtained as a result of division by the above-mentioned barrier; a means for arc firing.
 2. A gas-discharge switching device as claimed in claim 1, wherein the discharge chambers obtained as a result of division by the above-mentioned barrier communicate between each other. 